How easy is it to balance in each situation? As you do the activity, each step limits your sensory information more and more. The cushion limits information from the bottoms of your feet, standing on one foot limits information to only one foot and finally you eliminate visual information from your eyes. Your senses combine to your ability to balance. By holding your arms at your sides, you could no longer make small adjustments as your body lost its balance. As you move around you constantly use sensors to assess the position of the body and use that information to make the required adjustments to keep you from losing your balance.